Sails blueprints lifecycle - node.js

I need to add some additional data to result of find blueprint. I found this solution:
module.exports = {
find: function(req, res) {
return sails.hooks.blueprints.middleware.find(req, res);
}
}
but I can`t find any way to change response here, or add callback into the blueprint. I even try to change blueprint and add the cb in it:
module.exports = function findRecords (req, res, cb) {
...
if (typeof cb === 'function') res.ok(cb(result));
else res.ok(result);
but in this case it returns 500 statusCode every time (but with corresponding data)

I have been struggling with the same issue for a couple of time. Here is my hack (with explanation) to solve this.
The build in blueprint will always make a call to res.ok, res.notFound, or res.serverError if an error occurs. With altering of this method calls, it is possible to modify the output.
/**
* Lets expose our own variant of `find` in one of my controllers
* (Code below has been inserted into each controller where this behaviour is needed..)
*/
module.exports.find = function (req, res) {
const override = {};
override.serverError = res.serverError;
override.notFound = res.notFound;
override.ok = function (data) {
console.log('overriding default sails.ok() response.');
console.log('Here is our data', data);
if (Array.isArray(data)) {
// Normally an array is fetched from the blueprint routes
async.map(data, function(record, cb){
// do whatever you would like to each record
record.foo = 'bar';
return cb(null, record);
}, function(err, result){
if (err) return res.error(err);
return res.ok(result);
});
}
else if (data){
// blueprint `find/:id` will only return one record (not an array)
data.foo = 'bar';
return res.ok(data);
}
else {
// Oh no - no results!
return res.notFound();
}
};
return sails.hooks.blueprints.middleware.find(req, override);
};

Seems like only copy-paste solution existed. So I copy all code from files in node_modules/sails/lib/hooks/blueprints/actions to the actions of every controller and then change it.

Related

What is next() doing in this Express route and why is its order in the code important?

I'm getting confused with next(); I read through this post which essentially says it passes control to the next route. In my code below, having next(); where it is causes me to get "Cannot set headers after they are sent to the client". However, if I comment that out and then restore the else clause of my if statement, it functions correctly both when an incorrect empID is passed as well as when a correct one is. I'm hoping someone could explain what exactly is happening? Why does the position of the next() matter? It seems like it would be called either way?
I'm trying to do what is happening in this post which is add a value to, say req.user, but I haven't been able to get that to work at all so I'm trying the method I have here.
let checkEmp = (req, res, next) => {
db.get("select * from Employee where id = $id", {$id: req.empID},
(err, row) => {
if (err || row === undefined) {
res.status(404).send();
// } else {
// next();
}
});
next();
};
// get all timesheets
timesheetRouter.get("/", getParams, checkEmp, (req, res, next) => {
if (req.empID) {
db.all("select * from Timesheet where employee_id = $id", {$id: req.empID},
(err, rows) => {
if (err) {
next(err);
} else {
return res.status(200).send({timesheets: rows});
}
});
} else {
return res.status(404).send("Nothing to see here");
}
});
Looks like db.get() is probably asynchronous, so in the example as shown, next() will be called before db.get() finishes and it moves on to the next handler. Then, when the db.get() finishes, it tries to send a response, but the response has already been sent by the anonymous function in the main handler. By moving the next() inside of db.get(), you're essentially waiting for it to finish before moving on.

I'd like to follow the DRY principle and simplifying routing on this express server?

I have the following express server set up (server is just express() from another file). I am sure there is a way to simplify this to only one server.get() but I haven't been able to figure out how. Any help or points in the right direction would be appreciated.
module.exports.api = function (server, fs) {
server.get('/api/getData/:uuid', function (req, res) {
fs.readFile(__dirname + '/data.json', function (err, data) {
if (err) throw err;
data = JSON.parse(data);
data.forEach(function (match) {
match['uuid'] = match['x'] + '-' + match['y'];
});
var match = data.filter(function (e) {
return e.uuid == req.params.uuid
})[0];
res.send(200, match);
});
});
server.get('/api/getData', function (req, res) {
fs.readFile(__dirname + '/data.json', function (err, data) {
if (err) throw err;
data = JSON.parse(data);
data.forEach(function (match) {
match['uuid'] = match['x'] + '-' + match['y'];
});
res.send(200, data);
});
});
};
Here's a solution that just moves the common code into a shared function, yet still uses the two routes for routing clarity:
function getData(res, uuid) {
fs.readFile(path.join(__dirname, 'data.json'), function (err, fileData) {
if (err) {
return res.send(500);
}
let data = JSON.parse(fileData);
data.forEach(function(match) {
match['uuid'] = match['x'] + '-' + match['y'];
});
if (uuid) {
var match = data.filter(function (e) {
return e.uuid == uuid;
})[0];
}
res.send(200, match);
});
}
module.exports.api = function (server, fs) {
server.get('/api/getData/:uuid', function (req, res) {
getData(res, req.params.uuid);
});
server.get('/api/getData', function (req, res) {
getData(res);
});
};
This changes the following things:
Puts shared code into getData() function that is called from both routes.
Sends an error response if fs.readFile() has an error
Creates new local variable so it doesn't assign back to a function argument which is now a less desirable practice because it prevents some interpreter optimizations.
Uses path.join() to join parts of a path in a more cross platform way.
FYI, unless the data in data.json actually changes from time to time, you could just read this data into a variable once and then cache it rather than rereading it on every one of these requests.
Note: You could use routing wildcards and reduce your code to a single route, but this is mostly considered an anti-pattern because wildcards often match much more than you want, creating situations where you have manually trigger 404 errors for things you didn't intend to match that ended up matching your routing wildcard. So, it is considered a good thing to explicitly declare the routes you intend to match rather and just share the appropriate implementation code rather than trying to collapse things down to a single route that matches more than one form of URL.
There are, of course, always exceptions by remember that the goal is clear, correct, maintainable, reliable code, not necessarily the fewest number of routes.
If you just want to cache the data.json data at server start up time, you can use require() to load and parse it for you like this and then there's really no reason for the sharef fucntion:
const cacheData = require('./data.json');
cacheData.forEach(function(match) {
match['uuid'] = match['x'] + '-' + match['y'];
});
module.exports.api = function (server, fs) {
server.get('/api/getData/:uuid', function (req, res) {
let match = cacheData.filter(function (e) {
return e.uuid == req.params.uid;
})[0];
res.send(match);
});
server.get('/api/getData', function (req, res) {
res.send(cacheData);
});
};

Node, mongo and loop, how to break loop when I find data

My code looks similar to that:
var mongo_client = require('mongodb').MongoClient, dataStorage;
lib = {
[...]
find: function(res, param, callback) {
var parentPath = param.path;
while (parentPath !== '/') {
collection.findOne({'paths' : parentPath}, {...}, function(err, data)) {
if (data) {
dataStorage = data;
callback(data, res);
}
}
if (dataStorage) {
return;
}
parentPath = lib.removeLastBlockOfPath(parentPath);
}
if (!dataStorage) {
callback(someDefaultData, res);
}
}
[...]
}
What I want to do is to find some path stored in mongo, or if there is no match, try do find first matching parent path.
I can't set dataStorage value from findOne callback is it any way to do that? Eaven if I find path it always run thru all path blocks.
Node is asynchronous, so your code must be written accordingly. An option is to use the async module, that has lots of tools to manage asynchronous flows.
For example, you could use the whilst function to manage your while loop:
find: function(res, param, callback) {
var parentPath = param.path,
dataStorage = null;
async.whilst(
function () { return parentPath !== '/'; },
function (done) {
collection.findOne({'paths' : parentPath}, {...}, function(err, data) {
if (data) {
dataStorage = data;
return callback(data, res);
}
parentPath = lib.removeLastBlockOfPath(parentPath);
done();
});
},
function (error) {
if (!dataStorage) return callback(someDefaultData, res);
}
);
}
Don't forget to install and require the async module:
var async = require('async');
Your code is written as if it is "traditional synchronous" -- which its not. You cannot check for dataStorage validity till results from findOne() come back -- so your checks need to be moved all the way into the inner "if (data)" statement. This is not a mongodb issue, this is purely how nodejs works and the fact that everything is asynchronous and works on callbacks.

express & mongoose - Cannot call method 'get' of undefined - using res.json()

and thanks to be there.
Issue :
I'm making a tiny mongoose "middleware" to handle a mongoose error :
// callback function called at each mongoDB response
var handleDbRes = function(callback) {
return function (err, entries) {
if (err) {
err.status = 500;
return next(err);
}
return callback(entries) // that line throw the exception
}
};
And so I'm using it into an api endpoint, e.g. :
someRouter.get('/', function(req, res) {
models.article.find(handleDbRes(res.json))
})
With that code, I encounter an error :
TypeError: Cannot call method 'get' of undefined
I followed the exception and looked at res.json() declaration, when debugging, I figured out :
var app = this.app;
var *** = app.get('***') // that line throw the exception
I guess that app is not defined cause app doesn't exists in "this".
Please can you help me to solve this problem ? I think that the reason is simple but I don't get it...
Thanks you for listening ;)
EDIT : I tried to res.json.bind(res) and it worked, as I thought, but that's really awful to bind this way for most api endpoint and I guess there is another way to do that kind of functionality without that.
EDIT : Thanks to Mscdex advices, I modified my code this way :
.get('/', function(req, res, next) {
models.article.find(handleDbRes(res.json.bind(res), next))
...
...
// callback function called at each mongoDB response
var handleDbRes = function(successCallback, errorCallback) {
return function (err, entries) {
if (err) {
err.status = 500;
return errorCallback(err);
}
return successCallback(entries)
}
};
When you pass res.json, the context for the json() function is lost (it no longer knows what this is because it is not bound). So here are a few possible solutions:
Use a bound version of the function so that this inside json() will always evaluate correctly:
someRouter.get('/', function(req, res) {
models.article.find(handleDbRes(res.json.bind(res)))
})
Or use a wrapper function instead:
someRouter.get('/', function(req, res) {
function respondJSON(val) {
res.json(val);
}
models.article.find(handleDbRes(respondJSON))
})
Or just pass in res and call res.json() inside handleDbRes():
someRouter.get('/', function(req, res) {
models.article.find(handleDbRes(res))
})
// callback function called at each mongoDB response
var handleDbRes = function(res) {
return function(err, entries) {
if (err) {
err.status = 500;
return next(err);
}
res.json(entries);
}
};
The other problem is that handleDbRes() doesn't have access to next, so you need to also pass that function in for when you run into an error.

rendering results of multiple DB/mongoose queries to a view in express.js

given the async nature of mongoose (or sequelize, or redis) queries, what do you do when you have multiple queries you need to make before rendering the view?
For instance, you have a user_id in a session, and want to retrieve some info about that particular user via findOne. But you also want to display a list of recently logged in users.
exports.index = function (req, res) {
var current_user = null
Player.find({last_logged_in : today()}).exec(function(err, players) {
if (err) return res.render('500');
if (req.session.user_id) {
Player.findOne({_id : req.session.user_id}).exec(function(err, player) {
if (err) return;
if (player) {
current_user = player
}
})
}
// here, current_user isn't populated until the callback fires
res.render('game/index', { title: 'Battle!',
players: players,
game_is_full: (players.length >= 6),
current_user: current_user
});
});
};
So res.render is in the first query callback, fine. But what about waiting on the response from findOne to see if we know this user? It is only called conditionally, so I can't put render inside the inner callback, unless I duplicate it for either condition. Not pretty.
I can think of some workarounds -
make it really async and use AJAX on the client side to get the current user's profile. But this seems like more work than it's worth.
use Q and promises to wait on the resolution of the findOne query before rendering. But in a way, this would be like forcing blocking to make the response wait on my operation. Doesn't seem right.
use a middleware function to get the current user info. This seems cleaner, makes the query reusable. However I'm not sure how to go about it or if it would still manifest the same problem.
Of course, in a more extreme case, if you have a dozen queries to make, things might get ugly. So, what is the usual pattern given this type of requirement?
Yep, this is a particularly annoying case in async code. What you can do is to put the code you'd have to duplicate into a local function to keep it DRY:
exports.index = function (req, res) {
var current_user = null
Player.find({last_logged_in : today()}).exec(function(err, players) {
if (err) return res.render('500');
function render() {
res.render('game/index', { title: 'Battle!',
players: players,
game_is_full: (players.length >= 6),
current_user: current_user
});
}
if (req.session.user_id) {
Player.findOne({_id : req.session.user_id}).exec(function(err, player) {
if (err) return;
if (player) {
current_user = player
}
render();
})
} else {
render();
}
});
};
However, looking at what you're doing here, you'll probably need to look up the current player information in multiple request handlers, so in that case you're better off using middleware.
Something like:
exports.loadUser = function (req, res, next) {
if (req.session.user_id) {
Player.findOne({_id : req.session.user_id}).exec(function(err, player) {
if (err) return;
if (player) {
req.player = player
}
next();
})
} else {
next();
}
}
Then you'd configure your routes to call loadUser wherever you need req.player populated and the route handler can just pull the player details right from there.
router.get("/",function(req,res){
var locals = {};
var userId = req.params.userId;
async.parallel([
//Load user Data
function(callback) {
mongoOp.User.find({},function(err,user){
if (err) return callback(err);
locals.user = user;
callback();
});
},
//Load posts Data
function(callback) {
mongoOp.Post.find({},function(err,posts){
if (err) return callback(err);
locals.posts = posts;
callback();
});
}
], function(err) { //This function gets called after the two tasks have called their "task callbacks"
if (err) return next(err); //If an error occurred, we let express handle it by calling the `next` function
//Here `locals` will be an object with `user` and `posts` keys
//Example: `locals = {user: ..., posts: [...]}`
res.render('index.ejs', {userdata: locals.user,postdata: locals.posts})
});
Nowadays you can use app.param in ExpressJS to easily establish middleware that loads needed data based on the name of parameters in the request URL.
http://expressjs.com/4x/api.html#app.param

Resources